Process of making composite bimetallic articles.



. w."H. MILLER. 1 PROCESS 0F MAKING COMROSIIBUI L'LIC ARTICLES.

' APPucATloN man JUNE 2. Mns.

1,250,612', d mem ne@ 13,1917.

.Fig-.1. y( Fig. l

Bar ofmetal o /ow ce'bi of' expansion p/aced in mold f heated tby'Oxy-acetylene' flame to a @ng/1t red.

v 'Y l f A f/vuX/n a ents rink/ed on HQ Z'- y surface.ogflsar.y P 4 nF735., l. I

Swjvace ,0f h? layer 'of rnetal afb/gh c cient of' expansion y lcleaned. y

l [ngot rol/ed and annealed, I

" j Bar baght to fsing tm-er- 4 ature an a /ayeroa meta .of

m ofthe same composiz'zion p'oured on to thedes/red ,h/,c/fnesls.

` ybbl' of Indiana,

WILLIAM H. MILLER, OF FORT WAYNE, INDIANA,

COMPANY, A CORPORATION ASSIGNR T0 GENERAL ELECTRIC OF NEW YORK.

PROCESS OF MAKING COMPOSITE BIMETALLIC ARTICLES.

To all 'whom t may concern:

Be it known that I, WILLIAM H. MILLER, a citizen .of the United States,residing at Fort lVayne, in the county of Allen, State have inventedcertain new and useful Improvements in Processes of Making CompositeBimetallic Articles, of which the following is a specication.

y invention relates to a process of making composite bi-metallicarticles, and in particular to a process of uniting two dissimilar metalbodies having relatively different coeiiicients of expansion.Specically, the invention relates to a process for the manufacture ofthermostatic metal.

Thermostatic metal, as known in the art, is a composite bi-metallic'article made up of two metals of relatively different coefficients ofexpansion. In its best known form thermostatic metal consists of stripsor bars of two dissimilar metals having different co- ,efficients ofexpansion securely united to form mechanically a single metallic stripor bar. The union of the two dissimilar metals must be very firm towithstand the strains occasionedby the bending or warping of thecomposite metal article when subjected to changes in temperature. As faras I am aware, it has heretofore been generally customary to unite thetwo dissimilar metals.

by soldering or brazing, and considerable difficulty has beenexperienced in uniting the two metals so that they would not separate ortear apart at their junction. The particular object-of my presentinvention is to provide an improved process for the manufacture ofthermostatic metal, and in general to provide an improved process foruniting two dissimilar metals, and dissimilar metals having differentmelting points and different coeflicients of expansion. carrying out theinvention, I unite the .two dissimilar metals by an improved weldingprocess which I preferably carry out with an Oxy-acetylene fiame ortorch.' y The novel features of the invention which I believe to bepatentable are definitely indicated in the claims appended hereto. Theinvention itself will be best understood from the following descriptiontaken in conjunction with the accompanying drawing, in which: A

' Figures l, 2, 3 and 4 diagrammatically represent the principal stepsin my improved Specification of Letters Patent.

in particular two Y acetylene flame.

Patented Dec. 18, 1:91?.

Application filed June 26, 1916. Serial No. 105,847.

process of making composite bi-metallic articles;and Fig. 5 is atabulated outline of the process.

The most sensitive thermostatic metal is ference of coefficience ofexpansion is the greatest. Practicall the use of a special nickel-steelalloy having a relatively low coefficient of expansion and of a leadedbrass having a relatively high coefficient of expansion has been foundvery satisfactory. Since it is diiicult to roll a leaded brass, I havefound it desirable to use a lead-free brass when the composite metal isto be subjected to a rolling operatiom; although the coeficientofexpansion of a lead-free brass is relatively lower than that of aleaded brass. Thus, in carrying out my invention, I prefer to use thespecial nickel-steel alloy known as invar whose composition issubstantially as follows:

Nickel 35.5 17;. Carbon .18% Manganese .42%

The remainder being pure iron.

Invar has an extremely low coefficient of expansion, andwhen a strip orsheet of this metal is united with a strip or sheet of brass thedifference in the expansion and contraction of the invar and brass caussthe composite metal strip or sheet to curl under temperature changes,thus providing a temperature responsive or thermostatic member. In orderthat constant and continuous performance may be obtained from this.composite bi -metallic member, it is necessary that the two dissimilarmetals of which it is composed be as perfectly united as is possible,and the particular aim of the present invention is to provide a processfor unitinginvar and brass to produce-a satisfactory -therniostaticmetaL In carrying out the invention, as digramf inatically representedin Fig. 1, a bar of invar 5 of'suitable dimensions is placed in a mold 6made of refractory material held t0-v gether by a suitable binder. Thebar of invar is'yirst uniformly vheated to a bright red in the' moldpreferably by means of an oxy- A suitable fluxing agent, such forexample as powdered borax, is next sprinkled over the surface of theinvar and slide as it emerges allowed to fuse or melt. Starting at theupper end or end farthest away from the operator, the upper surface ofthe invar bar is then brought to a fusing temperature, and whilein thisstate brass is melted on by means of the Oxy-acetylene torch, and thusalloyed with the fused surface of the invar. This fusing and meltingoperation, or brassing as it is called in practice, is continued untilthe entire surface of the invar bar has received a uniform layer orcoating of brass to a thickness of about inch. This layer of brass isrepresented in Fig. 2 of the drawing by reference numeral 7.

A Crucible of molten brass is prepared in the meantime. At thecompletion of the brassing of the invar, the Oxy-acetylene fiame isplayed over the brassed surface of the invar until the surface of thebrass layer is in a molten condition. At this stage of the processsufficient molten brass from the crucible is poured into the mold andonto the brassed surface of the invar to produce the desired thicknessof brass in the composition ingot. Tn Fig. 3 of the drawing, the brassis represented by reference numeral 8. The ingot 5-8 thus obtained isthen allowed to remain in the mold until cool, when it may be removedand the process repeated forfadditional ingots. As previously stated,the brass used is preferably a lead-free brass, as the ingots aresubsequently subjected to rolling operations, and since rollingleaded-brass in a factory presents some difficulties on account ofcracking.

The composite ingot when removed from the mold is curved, and may bestraightened on a face plate with a hammer until the invar is absolutelystraight. The ingot is then placed in a suitable planer or shaper andcleaned up, care being taken to retain as much of the invar as possible.The brass is planed down to a thickness of about 20% greater than thethickness of the inval-,and `the sharp corners of the brass and invarare relieved or beveled to prelent excessive checkingof the edge of theingot in rolling. After shaping and cleaning, the composite ingot 5-8 ispassed through suitable rolls 9 and reduced to the desired thickness, asdiagrammatically represented in F ig. 4. In cold rolling it is necessaryto anneal and clean the piece a number of times. The rolling operationis carried out with the brass up, as the invar has a tendency to curveaway, from the brass side after vpassing through the rolls and wrapsitself around the roll. To prevent this, suitable landings or tables l0are placed close to the rolls on which the end of the ingot can strikeand from* the rolls, with the result that: only the extreme end of theingot is bent, while the remainder goes through the rolls straight. ltis also best to always nascere pass the ingot through the rolls in thesame way, since it .is thus much easier to keep the piece straight.

The annealing is carried out at a dull red heat, and it is onlynecessary to bring the metal to a uniform temperature, after which thepiece may be taken from the furnace and allowed to cool in the air. Ttis very necessary to thoroughly clean the piece after annealing andbefore again rolling, as the slightest scale or foreign matter on thesurface of the piece will roll out into large imperfections on thesurface of the finished article. plished by first pickling inhydrochloric acid until the scale on the invar has been loosened, thenscratch brushing the brass side on a bristle wheel with pumice stone andthe invar side on a brass wire wheel, and finally drying in hotsaw-dust.

By the improved process of my present invention a relatively thin layerof brass is first welded to the invar bar. A perfectly welded unionbetween the brass and invar is obtained by fusing at one time only arelatively small area of the fiuXed surface of the invar. By means ofthe Oxy-acetylene flame a small area of the fluXed surface of the invaris fused and a layer of brass melted thereon, whereby the whole of thissmall area under treatment can be easily heated to a uniform fusedstate, and a perfect weld obtained between the fused invar and themelted brass. This fusing and. melting operation, areas of the invar baris progressively eX- tended until the whole fluxed surface of thc barhas been so treated, whereby the whole layer of brass is perfectlywelded to the invar. T have found that the fused invar and melted brassalloy vto a certain extent, which further insures a perfect unionbetween the two dissimilar metals. t will The cleaning is bestV accomgor brassing, over small be evident that the brass is actually welded lfam acquainted, photomicrographs show a very definite line of demarcationbetween the two dissimilar metals.

iVhat T claim as new and desire to secure by Letters Patent of theUnited States, is'

article which comprises the consecutive steps of heating a body of metalcontained in a mold, applying a fiuxing agent to a l. The process ofmaking a loi-metallic.

Alayer of the second and pouring molten a fluxlng agent surface of theheated metal, fusing a small area of the luxed surface of said body ofmetal and melting .onto the fused area a relatively thin layer of asecond metal and progressively extending this fusing and meltingoperation over the Whole fluxed surface of said body of metal, andpouring molten metal of the same composition as said second metal uponsaid layer of the second metal.

2. The process of making a bi-metallic article Which comprises theconsecutive steps of fusing a small area of a surface of abody of metaland melting onto the fused area a relatively thin layer of a secondmetal and progressively extending this fusing and melting operation overthe Wholeof this surface of said body of metal, and pouring molten metalof the same composition as said second metal upon said layer of thesecond metal. v

3. The process of making a bi-metallic article which comprises theconsecutive steps of heating to a bright red a body of metal containedin a mold, applying a fluxing agent to a surface of the heated metal,fusing a small area of the fluxed surface of said body 'of metal andmelting onto the fused area a -relatively thinlayer of a second metalandV progressively extending this fusing and melting operation over theWhole, iiuxed surface of said body of metal, heating the resulting layerof Said second metal until its Whole surface is in a molten condition,and pouring molten metal of the same composition as said second metalupon said layer of the second metal.

4. The process of making a bi-metallic article which rcomprises theconsecutive steps of heating a body of metal, applying a fluxing agentto a surface of the heated metal, fusing the fluxed surface of the-metal and melting onto the fused surface a relatively thin-layer of asecond metal, and pouring molten metal of the same composition as saidsecond metal upon said layer of the second metal. l

of making a bi-metallic article Which consists in heating a body of oneof the metals of such article, fusing a surface of the heated metal andmelting Onto nthe fused surface a relatively thin metal of said article,

metal of the same compositionas said second metal upon said layer ofthesecond metal.

6. The process of making thermostatic metal which comprises theconsecutive steps of'heating a body of metal of low coelicient ofexpansion contained in a mold, applying 5. The process to a surface ofthe heated metal, fusing a small area of the Huxed surface of said bodyonto the fused area a relatively thin layer of a second metal ofrelatively high coefficient of expansion and progressively' extendingthis fusing and melting operation over the Whole luxed surface of saidbody of metal, and pouring molten metal of the same composition as saidsecond metal upon said layer of the second metal.

7. The process of making thermostatic metal comprising fusing a smallarea of a surface of a body of metal of 10W coefficient of expansion atone end thereof and melting onto the fused area a relatively thin layerof a second metal of relatively high coe'licient of expansion andprogressively extending this fusing and melting operation over the Wholeof this surface of said body of metal, and pouring molten metal of thesame composition as said second metal upon said layer of the secondmetal.

8. The process of making thermostatic metal which comprises theconsecutive steps of heating a bar of nickel-steel alloy contained in amold, applying a fiuxing agent to a surface of the heated alloy, fusinga small area of the luxed surface of said alloy and melting onto thefused area a relatively thin layer of brass and progressively extendingthis fusing and melting opera.- tion over the Whole iuxed area of saidalloy, and pouring molten brass upon said layer of brass.

9. The process of making thermostatic vmetal comprising fusing a smallarea of a surface of a bar of nickel-steel alloy and melting onto thefused area a relatively thin layer of brass and progressively extendingthis fusing and melting operation over the whole of this surface of saidalloy, and pouring molten brass upon said layer of brass.- e

10. The process ofmaking thermostatic metal which comprises theconsecutive steps of heating to a bright red a bar of nickelsteel alloycontained in a mold, applying a fluxing agent to a surface of the heatedalloy, fusing a small area of the `luxed surface of said alloy andmelting onto the fused area a relatively thin layer of brass andprogressively extending this fusing 'f and melting operation over theWhole fluxed surface of said alloy, heating the resulting layer ofbrassuntil its whole surface is in a molten condition, and pouringmolten brass upon said layer of brass.

In Witness whereof, I have hereunto set 'my hand'this 19 day of June1916.

WILLIAM H. MILLER.

of metal and melting

